Currently, typical power semiconductor devices, including devices such as high-voltage P-I-N diodes, power MOSFETs and insulated gate bipolar transistors (IGBTs), are fabricated with silicon (Si) semiconductor material. More recently, silicon carbide (SiC) power devices have been considered due to their superior properties. III-Nitride or III-N semiconductor devices, such as gallium nitride (GaN) devices, are now emerging as attractive candidates to carry large currents, support high voltages and to provide very low on-resistance and fast switching times. Although high voltage III-N diodes, transistors and switches are beginning to be commercialized, further improvements are needed in order to improve the efficiency and output characteristics of the devices. The term device will be used in general for any transistor or switch or diode when there is no need to distinguish between them.